2 * AppArmor security module
4 * This file contains AppArmor dfa based regular expression matching engine
6 * Copyright (C) 1998-2008 Novell/SUSE
7 * Copyright 2009-2012 Canonical Ltd.
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License as
11 * published by the Free Software Foundation, version 2 of the
15 #include <linux/errno.h>
16 #include <linux/kernel.h>
18 #include <linux/slab.h>
19 #include <linux/vmalloc.h>
20 #include <linux/err.h>
21 #include <linux/kref.h>
23 #include "include/apparmor.h"
24 #include "include/match.h"
26 #define base_idx(X) ((X) & 0xffffff)
29 * unpack_table - unpack a dfa table (one of accept, default, base, next check)
30 * @blob: data to unpack (NOT NULL)
31 * @bsize: size of blob
33 * Returns: pointer to table else NULL on failure
35 * NOTE: must be freed by kvfree (not kfree)
37 static struct table_header *unpack_table(char *blob, size_t bsize)
39 struct table_header *table = NULL;
40 struct table_header th;
43 if (bsize < sizeof(struct table_header))
46 /* loaded td_id's start at 1, subtract 1 now to avoid doing
47 * it every time we use td_id as an index
49 th.td_id = be16_to_cpu(*(u16 *) (blob)) - 1;
50 if (th.td_id > YYTD_ID_MAX)
52 th.td_flags = be16_to_cpu(*(u16 *) (blob + 2));
53 th.td_lolen = be32_to_cpu(*(u32 *) (blob + 8));
54 blob += sizeof(struct table_header);
56 if (!(th.td_flags == YYTD_DATA16 || th.td_flags == YYTD_DATA32 ||
57 th.td_flags == YYTD_DATA8))
60 tsize = table_size(th.td_lolen, th.td_flags);
64 table = kvzalloc(tsize);
66 table->td_id = th.td_id;
67 table->td_flags = th.td_flags;
68 table->td_lolen = th.td_lolen;
69 if (th.td_flags == YYTD_DATA8)
70 UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
72 else if (th.td_flags == YYTD_DATA16)
73 UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
75 else if (th.td_flags == YYTD_DATA32)
76 UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
80 /* if table was vmalloced make sure the page tables are synced
81 * before it is used, as it goes live to all cpus.
83 if (is_vmalloc_addr(table))
95 * verify_dfa - verify that transitions and states in the tables are in bounds.
96 * @dfa: dfa to test (NOT NULL)
97 * @flags: flags controlling what type of accept table are acceptable
99 * Assumes dfa has gone through the first pass verification done by unpacking
100 * NOTE: this does not valid accept table values
102 * Returns: %0 else error code on failure to verify
104 static int verify_dfa(struct aa_dfa *dfa, int flags)
106 size_t i, state_count, trans_count;
109 /* check that required tables exist */
110 if (!(dfa->tables[YYTD_ID_DEF] &&
111 dfa->tables[YYTD_ID_BASE] &&
112 dfa->tables[YYTD_ID_NXT] && dfa->tables[YYTD_ID_CHK]))
115 /* accept.size == default.size == base.size */
116 state_count = dfa->tables[YYTD_ID_BASE]->td_lolen;
117 if (ACCEPT1_FLAGS(flags)) {
118 if (!dfa->tables[YYTD_ID_ACCEPT])
120 if (state_count != dfa->tables[YYTD_ID_ACCEPT]->td_lolen)
123 if (ACCEPT2_FLAGS(flags)) {
124 if (!dfa->tables[YYTD_ID_ACCEPT2])
126 if (state_count != dfa->tables[YYTD_ID_ACCEPT2]->td_lolen)
129 if (state_count != dfa->tables[YYTD_ID_DEF]->td_lolen)
132 /* next.size == chk.size */
133 trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen;
134 if (trans_count != dfa->tables[YYTD_ID_CHK]->td_lolen)
137 /* if equivalence classes then its table size must be 256 */
138 if (dfa->tables[YYTD_ID_EC] &&
139 dfa->tables[YYTD_ID_EC]->td_lolen != 256)
142 if (flags & DFA_FLAG_VERIFY_STATES) {
143 for (i = 0; i < state_count; i++) {
144 if (DEFAULT_TABLE(dfa)[i] >= state_count)
146 if (base_idx(BASE_TABLE(dfa)[i]) + 255 >= trans_count) {
147 printk(KERN_ERR "AppArmor DFA next/check upper "
153 for (i = 0; i < trans_count; i++) {
154 if (NEXT_TABLE(dfa)[i] >= state_count)
156 if (CHECK_TABLE(dfa)[i] >= state_count)
167 * dfa_free - free a dfa allocated by aa_dfa_unpack
168 * @dfa: the dfa to free (MAYBE NULL)
170 * Requires: reference count to dfa == 0
172 static void dfa_free(struct aa_dfa *dfa)
177 for (i = 0; i < ARRAY_SIZE(dfa->tables); i++) {
178 kvfree(dfa->tables[i]);
179 dfa->tables[i] = NULL;
186 * aa_dfa_free_kref - free aa_dfa by kref (called by aa_put_dfa)
187 * @kr: kref callback for freeing of a dfa (NOT NULL)
189 void aa_dfa_free_kref(struct kref *kref)
191 struct aa_dfa *dfa = container_of(kref, struct aa_dfa, count);
196 * aa_dfa_unpack - unpack the binary tables of a serialized dfa
197 * @blob: aligned serialized stream of data to unpack (NOT NULL)
198 * @size: size of data to unpack
199 * @flags: flags controlling what type of accept tables are acceptable
201 * Unpack a dfa that has been serialized. To find information on the dfa
202 * format look in Documentation/security/apparmor.txt
203 * Assumes the dfa @blob stream has been aligned on a 8 byte boundary
205 * Returns: an unpacked dfa ready for matching or ERR_PTR on failure
207 struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags)
212 struct table_header *table = NULL;
213 struct aa_dfa *dfa = kzalloc(sizeof(struct aa_dfa), GFP_KERNEL);
217 kref_init(&dfa->count);
221 /* get dfa table set header */
222 if (size < sizeof(struct table_set_header))
225 if (ntohl(*(u32 *) data) != YYTH_MAGIC)
228 hsize = ntohl(*(u32 *) (data + 4));
232 dfa->flags = ntohs(*(u16 *) (data + 12));
237 table = unpack_table(data, size);
241 switch (table->td_id) {
243 if (!(table->td_flags & ACCEPT1_FLAGS(flags)))
246 case YYTD_ID_ACCEPT2:
247 if (!(table->td_flags & ACCEPT2_FLAGS(flags)))
251 if (table->td_flags != YYTD_DATA32)
257 if (table->td_flags != YYTD_DATA16)
261 if (table->td_flags != YYTD_DATA8)
267 /* check for duplicate table entry */
268 if (dfa->tables[table->td_id])
270 dfa->tables[table->td_id] = table;
271 data += table_size(table->td_lolen, table->td_flags);
272 size -= table_size(table->td_lolen, table->td_flags);
276 error = verify_dfa(dfa, flags);
285 return ERR_PTR(error);
289 * aa_dfa_match_len - traverse @dfa to find state @str stops at
290 * @dfa: the dfa to match @str against (NOT NULL)
291 * @start: the state of the dfa to start matching in
292 * @str: the string of bytes to match against the dfa (NOT NULL)
293 * @len: length of the string of bytes to match
295 * aa_dfa_match_len will match @str against the dfa and return the state it
296 * finished matching in. The final state can be used to look up the accepting
297 * label, or as the start state of a continuing match.
299 * This function will happily match again the 0 byte and only finishes
300 * when @len input is consumed.
302 * Returns: final state reached after input is consumed
304 unsigned int aa_dfa_match_len(struct aa_dfa *dfa, unsigned int start,
305 const char *str, int len)
307 u16 *def = DEFAULT_TABLE(dfa);
308 u32 *base = BASE_TABLE(dfa);
309 u16 *next = NEXT_TABLE(dfa);
310 u16 *check = CHECK_TABLE(dfa);
311 unsigned int state = start, pos;
316 /* current state is <state>, matching character *str */
317 if (dfa->tables[YYTD_ID_EC]) {
318 /* Equivalence class table defined */
319 u8 *equiv = EQUIV_TABLE(dfa);
320 /* default is direct to next state */
322 pos = base_idx(base[state]) + equiv[(u8) *str++];
323 if (check[pos] == state)
329 /* default is direct to next state */
331 pos = base_idx(base[state]) + (u8) *str++;
332 if (check[pos] == state)
343 * aa_dfa_match - traverse @dfa to find state @str stops at
344 * @dfa: the dfa to match @str against (NOT NULL)
345 * @start: the state of the dfa to start matching in
346 * @str: the null terminated string of bytes to match against the dfa (NOT NULL)
348 * aa_dfa_match will match @str against the dfa and return the state it
349 * finished matching in. The final state can be used to look up the accepting
350 * label, or as the start state of a continuing match.
352 * Returns: final state reached after input is consumed
354 unsigned int aa_dfa_match(struct aa_dfa *dfa, unsigned int start,
357 u16 *def = DEFAULT_TABLE(dfa);
358 u32 *base = BASE_TABLE(dfa);
359 u16 *next = NEXT_TABLE(dfa);
360 u16 *check = CHECK_TABLE(dfa);
361 unsigned int state = start, pos;
366 /* current state is <state>, matching character *str */
367 if (dfa->tables[YYTD_ID_EC]) {
368 /* Equivalence class table defined */
369 u8 *equiv = EQUIV_TABLE(dfa);
370 /* default is direct to next state */
372 pos = base_idx(base[state]) + equiv[(u8) *str++];
373 if (check[pos] == state)
379 /* default is direct to next state */
381 pos = base_idx(base[state]) + (u8) *str++;
382 if (check[pos] == state)
393 * aa_dfa_next - step one character to the next state in the dfa
394 * @dfa: the dfa to tranverse (NOT NULL)
395 * @state: the state to start in
396 * @c: the input character to transition on
398 * aa_dfa_match will step through the dfa by one input character @c
400 * Returns: state reach after input @c
402 unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int state,
405 u16 *def = DEFAULT_TABLE(dfa);
406 u32 *base = BASE_TABLE(dfa);
407 u16 *next = NEXT_TABLE(dfa);
408 u16 *check = CHECK_TABLE(dfa);
411 /* current state is <state>, matching character *str */
412 if (dfa->tables[YYTD_ID_EC]) {
413 /* Equivalence class table defined */
414 u8 *equiv = EQUIV_TABLE(dfa);
415 /* default is direct to next state */
417 pos = base_idx(base[state]) + equiv[(u8) c];
418 if (check[pos] == state)
423 /* default is direct to next state */
424 pos = base_idx(base[state]) + (u8) c;
425 if (check[pos] == state)